A method of controlling an automobile air conditioner has been known in which heating or cooling of air is controlled by an air conditioner and a switch door in the path of the air is switched between a position enabling the circulation of inside-air and a position enabling the introduction of outside-air (See U.S. Pat. No. 3,315,730). However, in such a prior art method, only a limited number of variables are detected to determine the swtiching between the circulation of inside-air and the introduction of outside-air. Accordingly, such a prior art method cannot comply with the requirement that the air conditioning for a vehicle should be controlled by taking into account various factors associated with the operational condition of the vehicle, including the engine warm-up operation of the vehicle, the state of the air conditioning of the passenger compartment of the vehicle and the temperature at any time of the year.